Depression Can Be Bad for Your Physical Health, New Study of Americans Over 70 Shows

Depression, in older people, can be as dangerous to one's health as smoking. Older Americans who have symptoms of depression are as likely as those who smoke to develop a new disease within two years, according to a U-M study involving more than 6,000 Americans 70 years of age or older.

Caroline Blaum

The study, presented at the annual meeting of the Gerontological Society of America in November, 1999, was conducted by Caroline S. Blaum, assistant professor of internal medicine. It is based on data from the U-M Health and Retirement Study, funded by the National Institute on Aging.

"The relationship of depression, disease and disability is complex," says Blaum, who is also an assistant research scientist at the U-M Institute of Gerontology. "Not only do disease and disability lead to depressive symptoms, but depressive symptoms seem to be a precursor of the development of future disease. This effect is seen with relatively mild depressive symptoms such as decreased energy and restless sleeping, not just severe clinical depression."

To evaluate the link between disease and depressive symptoms, Blaum analyzed data collected from the same group of older people in 1993 and again in 1995. The population-based study contains extensive information on physical, mental, financial, and emotional health, as well as a wide range of demographic and behavioral information for a nationally representative sample of Americans born in 1923 or before.

At the start of the study, the average age of respondents was 77 years. Approximately 62 percent were female, and 87 percent were white. Respondents had an average of 2.1 chronic diseases each. Between 1993 and 1995, Blaum found, 48 percent reported that they had developed new diseases, while 52 percent had the same self-reported "disease burden" with which they started the study.

Controlling for gender, marital status, education, the number of diseases at the start of the study, and the presence of mental or sensory impairments and disabilities, Blaum analyzed how age, race, body mass index, smoking, physical limitations and depressive symptoms were related to the odds of developing a new disease during the two-year period. The types of diseases included the most common chronic conditions of older adults, such as diabetes, stroke, arthritis, and cardiac disease.

Physical limitations, such as limitations in the ability to walk several blocks, climb stairs, or lift a 10-pound object, were the strongest predictors that a person would develop a new disease two years later, increasing the odds of developing at least one new disease by nearly 50 percent. But older people who smoked or had multiple symptoms of depression such as feeling lonely or sad in the past week were 34 percent more likely than those who did not to develop new disease, according to Blaum's analysis.

"Other recent studies have suggested that depression and its symptoms are risk factors for cognitive decline and cancer," says Blaum. "This study suggests that depressive symptoms may represent pre-clinical indicators of a wide range of future diagnosed diseases. Along with obesity and smoking, symptoms of depression may be a potentially modifiable risk factor for increased disease burden in older people. Clinical trials are needed to find out whether treatment of mild depression leads to decreased disease burden and improved function in older adults."
Blaum can be reached at cblaum@umich.edu.